The present invention relates to an optical disk drive, which is capable of converging laser beam on a recording surface of an optical disk so that information can be written on and read from the recording surface.
Generally, an optical pickup used in an optical disk drive, which records optical information in an optical disk as a recording medium such as a CD (compact disk) and a DVD (digital versatile disk) and reads such optical information from the optical disk, is configured to converge laser beam emitted from a semiconductor laser on a recording surface of the optical disk. Specifically, the laser beam emitted from the semiconductor laser is deflected perpendicularly by a vertical reflection mirror toward the optical disk. The vertical reflection mirror is mounted on a carriage which is movable in a direction to track the optical disk. The deflected laser beam is then converged on the recording surface of the optical disk by an objective optical system. It is noted that the semiconductor laser may be mounted on the carriage, although it may be mounted in a fixture along with a collimator lens which converts the laser beam into parallel light so that the parallel light is emitted in parallel with the tracking direction of the optical disk toward the vertical reflection mirror. It is further noted, however, it has become a mainstream design to configure the optical pick up without a collimator lens and an objective lens to be a finite optical system while the entire optical components of the optical pickup are mounted on the carriage so that the entire optical disk drive can be downsized.
An example of such an optical pickup being entirely mounted on a carriage is disclosed in Japanese Patent Provisional Publication No. HE110-177735. FIG. 6 shows a cross-sectional view of a configuration of the optical pickup in an optical disk drive 200 which is entirely mounted on the carriage 106 taken from a plane being perpendicular to a direction of the carriage 106 to be moved. In FIG. 6, the carriage 106 is slidably supported by a pair of slide rails 108, 109 which are arranged parallel to an optical disk D and fixed to a fixture (not shown) of the optical disk drive 200 while the optical disk D is clamped to a spindle (not shown). More specifically, the carriage 106 is configured to be slidable only in a direction parallel to a tracking direction of the optical disk D so that a center of an objective lens 103 travels only in the tracking direction of the optical disk D.
The objective lens 103 is arranged on the carriage 106 to face the optical disk D through an opening provided on an upper surface of the carriage 106 with an optical axis thereof being oriented to be perpendicular to the optical disk D. On a side of the objective lens 103 on the carriage 106, a semiconductor laser 110 to emit laser beam, which is to be converged on a recording surface of the optical disk D by the objective lens, is arranged. Further, a vertical reflection mirror 102 is provided so that an axis of the laser beam emitted from the semiconductor laser 110 is deflected in a direction coinciding with the optical axis of the objective lens 103, and the deflected laser beam enters the objective lens 103.
With the above configuration, if the vertical reflection mirror 102 is arranged in an orientation wherein the laser beam is emitted from the semiconductor laser 110 in parallel with the optical disk D to enter the vertical reflection mirror 102 (similarly to a configuration of the optical pickup wherein a semiconductor laser as well as a collimator lens are mounted on a fixture), the vertical reflection mirror 102 can be configured to be inclined at 45 degrees with respect to the optical disk D in order to simply deflect the laser beam at 90 degrees. However, as shown in FIG. 6, an outer diameter of a package of the semiconductor laser 110 is generally considerably greater than a diameter of a beam spot of the laser beam entering the vertical reflection mirror 102. Therefore, in order to arrange the semiconductor laser 110 to emit the laser beam being parallel with the optical disk D at a center of the vertical reflection mirror 102, the package of the semiconductor laser 110 is required to partially protrude downward below a lower edge of the vertical reflection mirror 102. In the optical disk drive 200 shown in FIG. 6, in order to avoid the package of the semiconductor laser 110 from protruding, the semiconductor laser 110 is inclined with respect to the optical disk D so that the semiconductor laser 110 can be located closer to the optical disk D, and thus the entire height of the carriage 106 can be reduced.
In the configuration disclosed in the above-referenced publication, however, an inclination angle of the semiconductor laser 110 is limited, thus an inclination of the beam emitting from the semiconductor laser to the vertical reflection mirror 102 is also limited. Particularly, when a distance between the semiconductor laser 110 and the vertical reflection mirror 102 is longer, the semiconductor laser 110 can be located closer to the optical disk D even if the package of the semiconductor laser 110 is inclined at a smaller angle. As a result, an inclination angle between the vertical reflection mirror 102 and the optical disk D cannot be configured to be considerably smaller than 45 degrees. Therefore, an area to be occupied by the vertical reflection mirror 102 taken from a direction perpendicular to the optical disk D remains greater, and the height of the carriage 106 is not considerably reduced. Further, when the optical lens 103 is configured to be a finite optical system wherein divergent light is entered, the optical property of the beam may be deteriorated as the objective lens 103 is moved for focusing.